Effect of manganese and exposure to elevated temperature on the corrosion of twin-roll cast Al-Mg alloys

摘要

The effect of the addition of manganese and chromium on the corrosion behaviour of AlMg3 and AlMg4.5 twin-roll cast alloys was studied. The influence of Mn and long exposure to elevated temperature on alloy susceptibility to intergranular corrosion was assessed. The presence of Mn in both Al-Mg alloys significantly improves their resistance to intergranular corrosion, especially in the alloy with high Mg content. Exposure to elevated temperatures amplifies the corrosion attack of grain boundaries only in the alloys without Mn and Cr. The presence of Mn facilitates the bonding of Mg atoms in constituent particles and precipitates resulting in reduced amount of Mg available for precipitation on grain boundaries. The lack of beta-Al_3Mg_2 precipitation on grain boundaries is the cause of alloys low susceptibility to intergranular corrosion.